I'm shocked, but both admincd and minimal install ISO don't seem to support booting under UEFI. The ISOs do have a partition table, but fdisk -l doesn't show an EFI partition. Inside install-amd64-minimal-20141204.iso, I find a file called gentoo.efimg and a folder called gentoo.efimg.mountPoint but there's no hint on how to use them. Reproducible: Always
*** This bug has been marked as a duplicate of bug 370331 ***